One set of proposed experiments is aimed at the detection of gene derepression in trisomic human cells. In another project, the plasma levels of enzymes involved in purine metabolism are measured in women with breast cancer and in control subjects. A third program is concerned with the nutrition and biochemistry of mutant clones (of cultured erythroleukemic cells) which are resistant to halogenated pyrimidines. Finally, experiments are proposed which explore the biochemical mechanism whereby drugs that structurally resemble the natural pyrimidines affect level of arousal. The response of animals to these drugs, and to related substances, as well as the chemistry and anabolism of barbituric acid, is being investigated.